In conventional communication networks, no matter a fixed communication network, a Global System of Mobile communication network (GSM) or a Code Division Multiple Access (CDMA) mobile communication network, when a calling subscriber calls a called subscriber, under the condition that the called terminal is idle and there is no reply from the called subscriber, the network system will play a traditional ring back tone, i.e. “toot . . . toot . . . ”, stored in the terminating switching device to the calling subscriber.
FIG. 1 shows architecture of a conventional GSM mobile communication network. As shown in FIG. 1, a GSM mobile communication network comprises a calling terminal A corresponding to a calling subscriber, a called terminal B corresponding to a called subscriber, an Originating Mobile Switching Center (O_MSC) and a Terminating Mobile Switching Center (T_MSC), as well as a Home Location Register (HLR). Here, the O_MSC and the T_MSC refer to an originating switching device and a terminating switching device respectively.
FIG. 2 illustrates a flowchart of a method for providing ring back tones in a conventional GSM mobile communication network. As shown in FIG. 2, when the calling subscriber dials telephone number of called terminal B of the called subscriber via calling terminal A, in step 201, the O_MSC requests for roaming number of the called subscriber from the HLR to which the called terminal is attached after receiving a call request from mobile terminal A.
In steps 202 to 204, the HLR sends a message for requesting called roaming number to the T_MSC. The T_MSC distributes a roaming number for the called subscriber, i.e. MSRN, and returns the number to the HLR which returns the MSRN of the called subscriber to the O_MSC afterwards.
In step 205, the O_MSC sends an Initial Address Message (IAM) to the T_MSC. In step 206, after receiving the IAM from the O_MSC, the T_MSC pages the called subscriber, which means sending rings to mobile terminal B of the called subscriber, and then sends current state of called terminal B to the O_MSC via an Address Complete Message (ACM). Here, the state of called terminal B may be idle, busy, shutdown or out of service range.
The T_MSC determines state of called terminal B in step 207, and in step 208 plays a traditional ring back tone to calling terminal A via the O_MSC under the condition the called terminal is idle, or plays corresponding voice prompt to calling terminal A via the O_MSC if the called terminal is busy, shutdown or out of service range etc.
In step 209, after the called subscriber picking up and answering the phone, called terminal B sends an Answer Message (ANM) to the T_MSC. Then, the T_MSC sends an ANM to the O_MSC, stops playing ring back tone, and establishes a communication channel between calling terminal A and called terminal B.
Although being able to play ring back tones to calling subscribers, the prior art described above has the following shortcomings.
First, the ring back tones implemented in the prior art are solely and tedious sounds of “toot . . . toot . . . ”, which can hardly satisfy the individuation requirements for ring back tones, and will even limit the development in service quality provided by communication service providers.
Secondly, in the prior art, when a calling subscriber initiates a call to a called subscriber, all the rings played for the calling subscriber are uniform and tedious sounds of “toot . . . toot . . . ”, which means the prior art cannot provide different ring back tones corresponding to various called subscribers for the calling subscriber, making it difficult for a calling subscriber to distinguish different called subscribers according to the ring back tones.
Thirdly, because of making tedious sounds of “toot . . . toot . . . ” as uniform and exclusive ring back tone, the subscribers are not capable of customizing their favorite music or voices as the ring back tones, which is incompatible with individuation requirements of the subscribers, and limits service functions of the communication network, making it difficult for a subscriber to enjoy plentiful and free services.
In a word, in the system and the method for providing ring back tones in prior art, all ring back tones are played by switching devices, and they are exclusively uniform and tedious for different calling and called subscribers, therefore, the prior services can neither satisfy individuation requirements of different subscribers, nor distinguish various subscribers only based on ring back tones. Anyway, the prior art can no longer satisfy needs of subscribers for higher quality of communication service, and limits the development of the whole communication services.